The present invention relates to automatic transmission for a motor vehicle.
When in first gear or when driving at low speed, releasing the accelerator pedal causes engine braking to act strongly and uncomfortable drive feeling. Many measures have been proposed to overcome this defect, as disclosed in Japanese Patent Laid-Open Appln. No. 75844/1985.
When the vehicle with the conventional automatic transmission is running at a low speed on a steep declining road, it becomes difficult to fully control the vehicle speed by only the engine brake set at only low gear ratio. That is, much use of the brakes is made, and fade tends to occur.
Another possible countermeasure is to couple a lock up clutch with an one-way clutch in the transmission. However, this increases an entire length of the transmission.
As still another measure, the same applicant has previously proposed the automatic transmission having two parallel counter shafts. These counter shafts are respectively provided with first- and second-gear stages and third- and fourth-gear stages. Space of a reverse gear unit in this transmission is used for a fourth gear. Therefore engine braking may be selectively utilized without increasing the entire length of the transmission.
In this transmission, however, these still remains the problems relating to strength and durability of transmission elements due to inertial force. These problems in the prior art will be described more fully hereinafter referring to drawings.